Datasheet

SLVA037A
8 Designing a USB Power Distribution System Using the TPS2014 and TPS2015 Power Distribution Switches
This limitation makes it very difficult to use a PTC resistor as the overcurrent protection device in
a ganged configuration. The higher resistance of this device makes it impossible to meet the DC
voltage regulation.
The input, output, and bulk capacitors are selected for the same reasons as those selected for
the non-ganged design. The main difference is that the ferrite beads in this design are required
to meet the hot-insertion voltage droop requirement, as discussed in section 3.1.3.
Figure 3. Self-Powered Hub Ganged Reference Design
PCB layout is also very important. Consider the following recommendations:
• Place a ground plane under all circuitry to lower both resistance and inductance and
improve DC and transient performance.
• Place cuts in the ground plane between ports to help reduce the coupling of transients
between ports.
• Locate the output tantalum capacitor as close as possible to the USB connector to lower
impedance (mainly inductance) between the port and the capacitor and improve transient
load performance.
• Locate the TPS2014/15 as close as possible to the output port to limit switching noise.
• Locate the ceramic bypass capacitors as close as possible to the IN pins of the
TPS2014/15.